DMT symbol repetition in the presence of impulse noise

ABSTRACT

With the current initialization procedures defined in the VDSL and ADSL standards, even though the xDSL system could operate in Showtime in an impulse noise environment where symbols are being corrupted, the transceivers would not be able to reach Showtime because initialization would fail due to initialization message failure. Through the use of an improved initialization procedure for communication systems, operation in environments with higher levels of impulse noise is possible.

RELATED APPLICATION DATA

This application is a Continuation of U.S. Application Ser. No.15/479,866, filed Apr. 5, 2017, which is a Continuation of U.S.application Ser. No. 14/559,156, filed Dec. 3, 2014, now U.S. Pat. No.8,913,649, which is a Continuation of U.S. application Ser. No.12/769,747, filed Apr. 29, 2010, now U.S. Pat. No. 8,913,649, which is aContinuation of U.S. application Ser. No. 11/575,598, filed Mar. 20,2007, now U.S. Pat. No. 7,769,705, which is a national stage applicationunder 35 U.S.C. 371 of PCT Application No. PCT/US2005/036815, filed Oct.14, 2005, which claims the benefit of and priority under 35 U.S.C. §119(e) to U.S. Patent Application No. 60/619,618, filed Oct. 15, 2004,entitled “xDSL Initialization in the Presence of Impulse Noise,” each ofwhich are incorporated herein by reference in their entirety.

BACKGROUND Field of the Invention

This invention generally relates to communication systems. Morespecifically, an exemplary embodiment of this invention relates to aninitialization technique for communication systems. Another exemplaryembodiment relates to error detection and correction duringinitialization.

Description of Related Art

Communication systems often operate in environments with impulse noise.Impulse noise is a short-term burst of noise that is higher than thenormal noise that typically exists in the communication channel. Forexample, DSL systems operate on telephone lines and experience impulsenoise from many external sources including telephones, AM radio, HAMradio, other DSL services on the same line or in the same bundle, otherequipment in the home, etc. It is common practice for communicationsystems to use interleaving in combination with Forward Error Correction(FEC) to correct the errors caused by the impulse noise during user datatransmission, i.e., SHOWTIME.

SUMMARY

Standard initialization procedures in xDSL systems, such as thosespecified in ADSL ITU G.992 standards and VDSL ITU G.993 standards, aredesigned to optimize performance, such as data rate/reach, in thepresence of “stationary” crosstalk or noise. Impulse noise protection ishandled with Interleaving/FEC during data transmission mode, known as“SHOWTIME” in ADSL and VDSL systems, but the current xDSL initializationprocedures, also known as “training procedures,” are not designed tooperate in an environment with high levels of impulse noise. As anexample, there are several messages exchanged during initialization inADSL and VDSL ITU standards that are not designed to work well in anenvironment with high levels of impulse noise. For example, in the ADSL2G.992.3 standards, there are initialization messages such as R-MSG-FMT,C-MSG-FMT, R-MSG-PCB, C-MSG-PCB, R-MSG1, C-MSG1, R-MSG2, C-MSG2,R-PARAMS, C-PARAMS, etc., which use modulation techniques that do notprovide high levels of immunity to impulse noise. Likewise, for example,in the VDSL1 G.993.1 standards, there are initialization messages suchas O-SIGNATURE, O-UODATE, O-MSG1, O-MSG2, O-CONTRACT, O-B&G, R-B&G,R-MSG1, R-MSG2, etc., which use modulation techniques that do notprovide high levels of immunity to impulse noise. Additionally, G.994.1(G.hs), which is used as part of the initialization procedure for mostxDSL standards, uses modulation techniques that do not provide highlevels of immunity to impulse noise. In particular, a receiver will notbe able to correctly demodulate/decode the message information when only1 DMT symbol is corrupted by impulse noise. This is especiallyproblematic because xDSL systems are generally designed to be able topass steady-state (“SHOWTIME”) data without errors in the presence ofimpulse noise by configuring a parameter called Impulse Noise Protection(INP). INP is defined in the ADSL2 and VDSL2 standards as the number ofconsecutive DMT symbols that, when completely corrupted by impulsenoise, can be completely corrected by the receiver using FEC andinterleaving during SHOWTIME. For example, if INP=2, then if 2 (or less)SHOWTIME DMT symbols are corrupted by impulse noise, the interleavingand FEC coding will be configured to be able to correct all theresulting bit errors. This means that with the current initializationprocedures defined in the VDSL and ADSL standards, even though the xDSLsystem could operate in SHOWTIME in an impulse noise environment where 2DMT symbols are being corrupted, the transceivers would not be able toreach SHOWTIME because initialization would fail due to initializationmessage failure.

Accordingly, an exemplary aspect of this invention relates to animproved initialization procedure for communication systems that operatein environments with higher levels of impulse noise.

More specifically, an exemplary aspect of this invention relates to aninitialization sequence where the messages exchanged duringinitialization are designed to operate in environments with higherlevels of impulse noise.

Additional exemplary aspects of the invention relate to repeating DMTsymbols within initialization messages.

Additional exemplary aspects of the invention relate to duplicating andrepeating DMT symbols within initialization message(s).

Additional exemplary aspects of the invention relate to copying andrepeating DMT symbols within initialization message(s).

Additional exemplary aspects of the invention relate to repeating thetransmission of DMT symbols that are used to modulate initializationmessage information bits to correctly receive the messages in anenvironment with impulse noise.

Further exemplary aspects of the invention relate to using forward errorcorrection to encode and decode initialization messages duringinitialization.

Aspects of the invention further relate to using forward errorcorrection and interleaving to encode and decode initialization messagesduring initialization.

Still further aspects of the invention relate to using error detectiontechniques such as Cyclic Redundancy Checksum (CRC) on portions of aninitialization message during initialization.

Additional exemplary aspects of the invention relate to using errordetection techniques, such as CRC on portions of the bits in aninitialization message to correctly determine which DMT symbols arecorrupt.

Aspects of the invention also relate to utilizing error detectiontechniques, such as CRC, on portions of the bits in an initializationmessage to determine which bits are in error in a long message.

Aspects of the invention also relate to analyzing initialization messagelength to dynamically determine the type(s) of initialization messageerror detection and correction to be used.

Further aspects of the invention relate to using error detectiontechniques, such as CRC, on portions of the bits in an initializationmessage and message retransmission to correctly receive messages duringinitialization.

Additional exemplary aspects of the invention also relate to utilizingerror detection techniques such as CRC on portions of the bits in anymessage or signal to determine which DMT symbols are corrupted byimpulse noise during initialization.

Additional exemplary aspects of the invention relate to transmittingand/or receiving repeated DMT symbols with at least one CRC bit on eachDMT symbol.

These and other features and advantages of this invention are describedin, or are apparent from, the following detailed description of theexemplary embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The exemplary embodiments of the invention will be described in detail,with reference to the following figures wherein:

FIG. 1 is a functional block diagram illustrating an exemplaryembodiment of this invention;

FIG. 2 is a flowchart outlining an exemplary embodiment for initializinga communication system according to this invention; and

FIG. 3 is a flowchart outlining a second exemplary embodiment forinitializing a communication system according to this invention;

FIG. 4 is a flowchart outlining a third exemplary embodiment forinitializing a communication system according to this invention;

FIG. 5 is a flowchart outlining a fourth exemplary embodiment forinitializing a communication system according to this invention; and

FIG. 6 is a flowchart outlining a fifth exemplary embodiment forinitializing a communication system according to this invention;

DETAILED DESCRIPTION

The exemplary embodiments of this invention will be described inrelation to initialization in a wired and/or wireless communicationsenvironment, such as a DSL communication system. However, it should beappreciated, that in general, the systems and methods of this inventionwill work equally well for any type of communication system or protocolin any environment.

The exemplary systems and methods of this invention will also bedescribed in relation to multicarrier modems, such as DSL modems andVDSL modems, and associated communications hardware, software andcommunication channels. However, to avoid unnecessarily obscuring thepresent invention, the following description omits well-known structuresand devices that may be shown in block diagram form or otherwisesummarized.

For purposes of explanation, numerous details are set forth in order toprovide a thorough understanding of the present invention. It should beappreciated however that the present invention may be practiced in avariety of ways beyond the specific details set forth herein.

Furthermore, while the exemplary embodiments illustrated herein show thevarious components of the system collocated, it is to be appreciatedthat the various components of the system can be located at distantportions of a distributed network, such as a telecommunications networkand/or the Internet, or within a dedicated secure, unsecured and/orencrypted system. Thus, it should be appreciated that the components ofthe system can be combined into one or more devices, such as a modem, orcollocated on a particular node of a distributed network, such as atelecommunications network. As will be appreciated from the followingdescription, and for reasons of computational efficiency, the componentsof the system can be arranged at any location within a distributednetwork without affecting the operation of the system. For example, thevarious components can be located in a Central Office modem (CO, ATU-C,VTU-O), a Customer Premises modem (CPE, ATU-R, VTU-R), a DSL managementdevice, or some combination thereof. Similarly, one or more functionalportions of the system could be distributed between a modem and anassociated computing device.

Furthermore, it should be appreciated that the various links, includingcommunications channel 5, connecting the elements can be wired orwireless links, or any combination thereof, or any other known or laterdeveloped element(s) that is capable of supplying and/or communicatingdata to and from the connected elements. The term module as used hereincan refer to any known or later developed hardware, software, firmware,or combination thereof that is capable of performing the functionalityassociated with that element. The terms determine, calculate andcompute, and variations thereof, as used herein are used interchangeablyand include any type of methodology, process, mathematical operation ortechnique. Transmitting modem and transmitting transceiver as well asreceiving modem and receiving transceiver are used interchangeablyherein.

FIG. 1 illustrates an exemplary communication system. Communicationsystem 10 comprises a first transceiver 100 and a second transceiver200. The transceivers 100 and 200 each comprise a DMT symbolreception/determination module 110, a majority voting module 120, a DMTsymbol inspection and selection module 130, a DMT symbol repetitionmodule 140, a FEC/interleaving module 150, an INP determination typemodule 160, a CRC module 170, a modulation/demodulation module 180 and atransmitter/receiver module 190. It should be appreciated that numerouscomponents of the transceiver have been omitted for clarity. However,the transceivers 100 and 200 can also include the standard components ofa typical communications device(s).

In general, the systems and methods of this invention will be describedin relation to transceivers in a DSL communications environment.However, it should be appreciated that the techniques illustrated hereincan be implemented into any wired or wireless communication system.

In accordance with a first exemplary embodiment, DMT symbols that areused to modulate initialization messages are sent a plurality of times.Due to this repeated transmission, if one or more of the DMT symbols arecorrupted by impulse noise, the transceiver receiving the DMT symbolscan still recover the information therefrom. More specifically, and incooperation with the DMT symbol repetition module 140, the majorityvoting module 120 and the modulation/demodulation module 180, a DMTsymbol is repeated without modification with the receiving transceiverusing a variety of detection/demodulation schemes to recover the messageinformation bits. For example, the receiving transceiver could use a“majority voting” scheme where each DMT symbol is demodulatedindependently and then the message information bits recovered byexamining how many DMT symbols carry the same bit pattern.Alternatively, for example, the DMT symbols could be examined by the DMTsymbol inspection and selection module 130 prior to demodulation in thefrequency or time domain and based on these signals, the transceiverthat received the DMT symbols, in cooperation with the DMT symbolinspection selection module 130, selects the most likely DMT symbol tobe correct. For example, if a DMT symbol was repeated four times and oneDMT symbol was corrupted by impulse noise, then the receivingtransceiver could examine the four DMT symbols in the frequency domainand clearly detect that one of the four symbols has very different phaseand/or amplitude characteristics than the other three DMT symbols. Basedon this difference, the receiving transceiver could discard the one DMTsymbol that is corrupt and use the remaining three DMT symbols todemodulate and recover the information. Moreover, in order to randomizethe signal transmitted from the transmitting transceiver, the repeatedDMT symbols can use phase or bit scrambling. With phase scrambling, therepeated DMT symbols can use different phase shifts on the subcarriersin order to randomize the signal. With bit scrambling, the informationbits can be scrambled prior to modulating the bits on the repeated DMTsymbols.

In accordance with another exemplary embodiment, the number of repeatedsymbols can be determined based on the SHOWTIME Impulse Noise Protection(INP) requirements. For example, if the SHOWTIME INP=2, then DMT symbolscarrying initialization messages would be repeated during initializationat least INP*2+1=5 times. This way, even if two DMT symbols werecorrupted by impulse noise, there would be three remaining uncorruptedDMT symbols received by the receiving transceiver. Then, for example,and with the cooperation of the majority voting module 120, a majorityvoting scheme could be applied to correctly demodulate and recover theDMT symbol(s) without errors. Other algorithms could also be used toderive the number of repeated DMT symbols from the INP value. Forexample, the number of repeated DMT symbols could be set to A*INP+Bwhere A and B are integers.

In accordance with an exemplary embodiment, and with the cooperation ofthe DMT symbol repetition/determination module 110, a receiving modemdetermines the number of repeated DMT symbols and informs thetransmitting modem thereof. For example, the receiving modem couldreceive an INP value from one or more of a second transceiver or amanagement system. Based on this received INP value, and in cooperationwith the DMT symbol repetition module 140, the number of repeated DMTsymbols (M) for initialization messages is determined. Thisdetermination may be based on impulse noise measurements made by thereceiving transceiver or may be based on the received INP value or both.For example, if the INP value is used, M may be equal to INP*2+1. Themessage indicating the determined number of repeated DMT symbols (M) isthen transmitted to a second transceiver. Therefore, duringinitialization, the message bits are modulated onto the M repeated DMTsymbols.

For example, in an alternative embodiment, a transmitting modem, withthe cooperation of the DMT symbol repetition/determination module 110,could determine the number of repeated DMT symbols and send a message tothe receiving modem indicating the value. This determination can bebased on impulse noise measurements, based on a received INP value, orboth. Moreover, a management system 205 could determine one or more ofthe INP value and the number of repeated DMT symbols and configure thetransceivers for their use. This determination could be based on impulsenoise measurements or may be based on the received INP value or both.

DSL systems often use FEC and interleaving during SHOWTIME to correcterrors from impulse noise. In accordance with an exemplary embodiment ofthis invention, and with the cooperation of the FEC/Interleaving module150, FEC can be utilized with or without interleaving to correct impulsenoise that may corrupt messages during the initialization process. Forexample, prior to modulating information bits of an initializationmessage, the message information bits could be encoded using any FECtechnique, such as Reed Solomon codes, hamming codes, convolution codes,trellis codes, turbo codes, LDPC codes, or the like. At the receivingmodem, the FEC coding could be used to correct errors from impulsenoise. For example, initialization messages could be encoded with a ReedSolomon code using the codeword size N=K+R bytes, containing K messageinformation bytes and R FEC check bytes. This code can correct R/2bytes. For example, if each DMT symbol is used to modulate 1 byte, and aR-S code with N=6 and R=4 is used, then the decoder at the receivingmodem would be able to correct R/2=2 bytes in each codeword. Thiscorresponds to correcting two DMT symbols, assuming each DMT symbolcarries one byte. This would lead to the ability of the receiving modembeing able to correctly recover the message information bits even ifimpulse noise corrupted two DMT symbols. Additionally, interleavingcould be used to provide better immunity to impulse noise. For example,interleaving of multiple codewords could be used to spread the errorsfrom impulse noise over multiple codewords thereby enabling thereceiving transceiver to correct impulse noise events that corrupt evenmore DMT symbols.

For example, two DMT symbols with N=6 and R=4 could be interleaved, incooperation with the FEC/interleaving module 150, by transmitting onebyte from the first codeword and then transmitting one byte from thesecond codeword and continuing to alternate transmission in this manner.In this case, assuming each DMT symbol carries one byte, an impulsenoise that corrupted four consecutive DMT symbols would be correctableby the receiver because four consecutive DMT symbols would always bedivided between two codewords with each codeword having the ability tocorrect two bytes, or two DMT symbols.

During initialization, messages of various lengths are transmittedbetween the two transceivers 100 and 200. Some of these messages arelonger than others with longer messages, due to their length, being moresusceptible to impulse noise corruption. In accordance with anotherexemplary embodiment, and in cooperation with the INP determination typemodule 160, the type of impulse noise protection can be determinedbased, for example, on the length of the message being transmitted. Forexample, long initialization messages, such as C/R-PARAMS in ADSL,C/R-B&G in VDSL and G.994.1 messages are particularly problematic whentransmitted in the presence of impulse noise. This is because when amessage is long, it is very likely that some portion of the message willbe corrupted by impulse noise and not be correctly recovered by thereceiving modem. Although conventional DSL systems use standard errordetection methods, such as CRC, CRC covers the entire message and doesnot provide any information regarding which bits, or DMT symbols, werecorrupted by the impulse noise. Thus, when a CRC error is detected in amessage in conventional DSL systems, the whole message is simply resentby the transmitting modem. However, in an environment with high impulsenoise, the retransmitted message could be received in error as well andthe retransmission process repeated without success. With thecooperation of the CRC module 170, additional error detection capabilitycan be added to messages to enable the location of bit errors in longermessages. For example, and in cooperation with the CRC module 170, aone-byte CRC could be determined for each byte of the message. The CRCbyte and the information could be modulated and transmitted, with thecooperation of the modulation/demodulation module 180 andtransmitter/receiver module 190, on one DMT symbol. In this example, oneDMT symbol is carrying two bytes.

At the receiving modem, the two bytes are demodulated and the CRC byteis used to detect if there was impulse noise corrupting the associatedDMT symbol. If the CRC indicates there are no errors, then the receivingmodem correctly received the message byte. If the CRC shows that thereare errors, then the receiving modem needs to receive the DMT symbolagain, with the cooperation of the DMT symbol reception module 140, inorder to correctly recover the information. In this example, one CRCbyte is transmitted with one information byte on each DMT symbol and thereceiver can demodulate the entire message in this manner.

If impulse noise has corrupted some of the DMT symbols in the longermessage, the message can be retransmitted and the receiving modemperform a CRC check on the previously corrupted DMT symbols to determineif they are now received without errors. Since impulse noise istypically uncorrelated with the transmitted message signal, it is highlylikely that different DMT symbols will be corrupted when the signal isretransmitted, which means that the receiving modem will probablyreceive the previously corrupted DMT symbols without errors the secondtime that the message is transmitted. In the unlikely event that thesame DMT symbols are still in error, the message could be retransmittedover and over until all DMT symbols are received without errors. It ispossible upon retransmission that the impulse noise will cause errors indifferent DMT symbols than in the previous transmission. Therefore, thereceiving modem could store the correctly recovered message bits for DMTsymbols from the previously received message. The receiver can alsostore all the previously received message bits that were receivedwithout error and simply utilize the retransmitted message to correctlydetermine the message bits and the DMT symbols that were in errorpreviously.

For example, the receiving modem can send a message to the transmittingmodem requesting the transmitting modem to retransmit only a portion ofthe message that was previously received in error.

While the examples above describe computing a CRC and adding a CRC byteto each byte in the message, a plurality of CRC bits could be computedfor any number of bits in the message and transmitted to a receivingmodem. Moreover, although the examples above describe modulating twobytes in each DMT symbol, any number of bits can be modulated on eachDMT symbol. Although the examples above describe transmitting one CRCbyte in every DMT symbol, any number of CRC bits can be modulated oneach DMT symbol including, but not limited to, CRC bits being carried ononly a subset of the DMT symbols. For this case, some DMT symbols maynot have any CRC bits. As an example, one CRC byte could be computed foreach four message bytes and each DMT symbol could carry one byte. Inthis case, the first four DMT symbols would be used to modulate themessage bytes and the fifth DMT symbol would carry the CRC byte. At thereceiving modem, the CRC would be used to detect if any of the five DMTsymbols were corrupted by impulse noise. If the CRC showed an error hasoccurred, then the retransmission techniques described above could beused.

In another exemplary embodiment, the DMT symbol repetition and errordetection capabilities are combined to combat impulse noise on thecommunications line. For example, if a DMT symbol is repeated M times,and a CRC byte is transmitted with every DMT symbol, then the receivingmodem could use the CRC byte to determine if each DMT symbol was beingcorrectly demodulated. In this case, a majority voting scheme, or otherfrequency/time domain impulse noise detection method, such as thosediscussed above, would not necessarily be required. One advantage ofthis method is that it may require repeating a fewer number of DMTsymbols. For example, if the impulse noise corrupts one DMT symbol, amajority-voting scheme, in conjunction with the majority voting module120, would require at least three DMT symbols to make a decision.However, if a CRC byte was sent with each DMT symbol, then only tworepeated DMT symbols would be necessary since the CRC, with theassistance of the CRC module 170, would correctly identify theuncorrupted DMT symbol and discard the corrupted DMT symbol. If the INPvalue was being used to determine the number of repeated DMT symbols,then this method may require repeating a fewer number of DMT symbols.For example, it may be necessary to only repeat INP+1 DMT symbols, asopposed to 2*INP+1 in the case where a CRC is not used. Illustratively,if INP=2, then it may be necessary to only transmit INP+1=3 repeated DMTsymbols since the CRC byte could be used to detect the one correct DMTsymbol and discard the two corrupted DMT symbols.

In accordance with an exemplary embodiment, the receiving modemdetermines the number of repeated DMT symbols and informs thetransmitting modem thereof. In this exemplary embodiment, an INP valueis received from a second transceiver or a management system 205. Thenumber of repeated DMT symbols (M) is determined for the initializationmessages in cooperation with the DMT symbol repetition module 140. Thisdetermination may be based on impulse noise measurements made by, forexample, a receiving transceiver, or may be based on the received INPvalue or both. For example, if the INP value is used, M may be equal toINP+1. A message is then transmitted, with the cooperation of thetransmitter/receiver module 190 to the transmitting modem indicating thedetermined number of repeated DMT symbols (M). Therefore, duringinitialization, the modem would receive messages wherein the messagebits are modulated onto the M repeated DMT symbols with each DMT symbolcontaining at least one CRC bit for error detection.

For the transmitting modem, the transmitting modem would receive amessage indicating the determined number of repeated DMT symbols and,during initialization, modulate at least one message bit onto a DMTsymbol and transmit the DMT symbol (M) times, wherein each DMT symbolcontains at least one CRC bit for error detection.

Alternatively, the transmitting modem could determine a number ofrepeated DMT symbols and send a message to the receiving modem. Asdescribed above, this determination could be based on impulse noisemeasurements or may be based on the received INP value or both.

Still alternatively, a management system could determine the number ofDMT symbols and configure the transceivers accordingly. As describedabove, this determination may be made based on impulse noisemeasurements made by the receiving transceiver or may be based on thereceived INP value or both. While the above-described exemplaryembodiments are illustrated independently of one another, it should beappreciated the various techniques can be combined in whole or in part.

FIG. 2 illustrates an exemplary initialization methodology andcommunication between first and second transceivers. More specifically,for the first transceiver, control begins in step S100 and continues tostep S110. In step S110, an INP value is determined or, for example,received from a management system or another transceiver.

Next, in step S120, the INP value is transmitted to the secondtransceiver. Then, in step S130, a value M is received by the firsttransceiver where M is the number of repeated DMT symbols forinitialization messages. Control then continues to step S140.

In step S140, and during initialization, the first transceiver modulatesat least one message bit onto the M repeated DMT symbols. Next, in stepS150, the M number of DMT symbols are transmitted to the secondtransceiver. Control then continues to step S160 where the controlsequence ends.

For the second transceiver, control begins in step S105 and continues tostep S115. In step S115 an INP value is received. Next, in step S125,the number of repeated DMT symbols (M) is determined for use ininitialization and the value M transmitted to the first transceiver.Then, in step S135, the second transceiver receives the M number ofrepeated DMT symbols. Control then continues to step S145 where thecontrol sequence ends.

As with the previously discussed embodiments, and while not specificallyillustrated in the flowchart, additional error detection capability canalso be added to initialization message(s) to enable the location of biterrors. For example, each DMT symbol could also include at least one CRCbit, which can be used to detect if the DMT symbol is received correctlyor in error. However, this embodiment is not limited thereto and anyerror detection technique in any configuration will work with theinvention.

FIG. 3 illustrates a second exemplary methodology and communicationbetween transceivers for initialization. More specifically, for thefirst transceiver, control begins in step S200 and continues to stepS210. In step S210, an INP value is determined or, for example, receivedfrom a management system or another transceiver. Next, in step S220, thenumber repeated DMT symbols (M) for initialization messages isdetermined and transmitted to a second transceiver. Then, in step S230,and during initialization, at least one message bit is modulated ontothe M repeated DMT symbols. Control then continues to step S240.

In step S240, the M symbols are transmitted to the second transceiver.Control then continues to step S250 where the control sequence ends.

For the second transceiver, control begins in step S205 and continues tostep S215. In step S215, the value for M is received. Next, in stepS225, the M number of DMT symbols are received. Control then continuesto step S235 where the control sequence ends.

As with the previously discussed embodiments, and while not specificallyillustrated in the flowchart, additional error detection capability canalso be added to initialization message(s) to enable the location of biterrors. For example, each DMT symbol could also include at least one CRCbit, which can be used to detect if the DMT symbol is received correctlyor in error. However, this embodiment is not limited thereto and anyerror detection technique in any configuration will work with theinvention.

FIG. 4 illustrates another exemplary initialization methodology andcommunication between transceivers. More specifically, for the firsttransceiver, control begins in step S202 and continues to step S204. Instep S204, an INP value is determined or, for example, received from amanagement system or another transceiver. Next, in step S206, the numberof repeated DMT symbols (M) for initialization messages is determinedand transmitted to a second transceiver. Then, in step S208, the Mnumber of DMT symbols are received. Control then continues to step S209where the control sequence ends.

For the second transceiver, control begins in step S201 and continues tostep S203. In step S203, M is received. Next, in step S205, and duringinitialization, at least one message bit is modulated onto the Mrepeated DMT symbols Then, in step S207, the M number of DMT symbols aretransmitted. Control then continues to step S211 where the controlsequence ends.

As with the previously discussed embodiments, and while not specificallyillustrated in the flowchart, additional error detection capability canalso be added to initialization message(s) to enable the location of biterrors. For example, each DMT symbol could also include at least one CRCbit, which can be used to detect if the DMT symbol is received correctlyor in error. However, this embodiment is not limited thereto and anyerror detection technique in any configuration will work with theinvention.

FIG. 5 illustrates another exemplary initialization methodologyaccording to this invention. In particular, control begins in step S300and continues to step S310. In step S310, the CRC to byte ratio isdetermined. Next, in step S320, one or more CRC bits are determined fora number of bytes or bits. Then, in step S330, the one or more CRC bitsare modulated in addition to additional information on a DMT symbol.Control then continues to step S340.

In step S340, the DMT symbol is demodulated and the one or more CRC bitsare used to detect errors. Next, in step S350, a determination is madewhether the CRC bits have revealed errors. If errors are present,control continues to step S360. Otherwise, control jumps to step S380where the control sequence ends.

In step S360, retransmission of one or more DMT symbols or portionsthereof are requested. Then, in step S370, the errored DMT symbols arediscarded. Control then continues back to step S350.

FIG. 6 illustrates another exemplary embodiment for communicationinitialization according to this invention. In particular, controlbegins in step S400 and continues to step S410. In step S410, an INPvalue is determined or, for example, received from a management systemor another transceiver. Next, in step S420, the number of repeated DMTsymbols M is determined for initialization messages. Then, in step S430,the value for the number of repeated DMT symbols is transmitted to, orreceived from, as appropriate, a second transceiver. Control thencontinues to step S440.

In step S440, one or more initialization messages are transmitted orreceived, as appropriate, wherein at least one message bit is modulatedonto a DMT symbol and the DMT symbol(s) is repeated M times with eachDMT symbol including at least one CRC bit. Next, in step S450, thecombination of CRC bit(s) and repeated DMT symbols are utilized toinsure integrity of the initialization message(s). Control thencontinues to step S460 where the control sequence ends.

While the above-described flowcharts have been discussed in relation toa particular sequence of events, it should be appreciated that changesto this sequence can occur without materially effecting the operation ofthe invention. Additionally, the exact sequence of events need not occuras set forth in the exemplary embodiments, but rather the steps can beperformed by one or the other transceiver in the communication systemprovided both transceivers are aware of the technique being used forinitialization. Additionally, the exemplary techniques illustratedherein are not limited to the specifically illustrated embodiments butcan also be utilized with the other exemplary embodiments.

The above-described system can be implemented on wired and/or wirelesstelecommunications devices, such a modem, a multicarrier modem, a DSLmodem, an ADSL modem, an xDSL modem, a VDSL modem, a linecard, testequipment, a multicarrier transceiver, a wired and/or wirelesswide/local area network system, a satellite communication system, amodem equipped with diagnostic capabilities, or the like, or on aseparate programmed general purpose computer having a communicationsdevice or in conjunction with any of the following communicationsprotocols: CDSL, ADSL2, ADSL2+, VDSL1, VDSL2, HDSL, DSL Lite, IDSL,RADSL, SDSL, UDSL or the like.

Additionally, the systems, methods and protocols of this invention canbe implemented on a special purpose computer, a programmedmicroprocessor or microcontroller and peripheral integrated circuitelement(s), an ASIC or other integrated circuit, a digital signalprocessor, a hard-wired electronic or logic circuit such as discreteelement circuit, a programmable logic device such as PLD, PLA, FPGA,PAL, a modem, a transmitter/receiver, any comparable means, or the like.In general, any device capable of implementing a state machine that isin turn capable of implementing the methodology illustrated herein canbe used to implement the various communication methods, protocols andtechniques according to this invention.

Furthermore, the disclosed methods may be readily implemented insoftware using object or object-oriented software developmentenvironments that provide portable source code that can be used on avariety of computer or workstation platforms. Alternatively, thedisclosed system may be implemented partially or fully in hardware usingstandard logic circuits or VLSI design. Whether software or hardware isused to implement the systems in accordance with this invention isdependent on the speed and/or efficiency requirements of the system, theparticular function, and the particular software or hardware systems ormicroprocessor or microcomputer systems being utilized. Thecommunication systems, methods and protocols illustrated herein can bereadily implemented in hardware and/or software using any known or laterdeveloped systems or structures, devices and/or software by those ofordinary skill in the applicable art from the functional descriptionprovided herein and with a general basic knowledge of the computer andtelecommunications arts.

Moreover, the disclosed methods may be readily implemented in softwarethat can be stored on a storage medium, executed on programmedgeneral-purpose computer with the cooperation of a controller andmemory, a special purpose computer, a microprocessor, or the like. Inthese instances, the systems and methods of this invention can beimplemented as program embedded on personal computer such as an applet,JAVA® or CGI script, as a resource residing on a server or computerworkstation, as a routine embedded in a dedicated communication systemor system component, or the like. The system can also be implemented byphysically incorporating the system and/or method into a software and/orhardware system, such as the hardware and software systems of acommunications transceiver.

It is therefore apparent that there has been provided, in accordancewith the present invention, systems and methods for initializingtransceivers. While this invention has been described in conjunctionwith a number of embodiments, it is evident that many alternatives,modifications and variations would be or are apparent to those ofordinary skill in the applicable arts. Accordingly, it is intended toembrace all such alternatives, modifications, equivalents and variationsthat are within the spirit and scope of this invention.

The invention claimed is:
 1. A multicarrier transceiver comprising: areceiver capable of determining a repetition rate for DMT (DiscreteMultitone Modulation) symbols; a transmitter capable of transmitting afirst message during initialization, wherein the message indicates therepetition rate; the receiver further capable of receiving a secondmessage during initialization, wherein DMT symbols in the second messageare repeated in accordance with the repetition rate indicated in thefirst message, wherein the message comprises a plurality of CRC (CyclicRedundancy Check) bits, and wherein at least one DMT symbol in thesecond message comprises one CRC byte and no information bits.
 2. Thetransceiver of claim 1, wherein the receiver is capable of determiningthe repetition rate based on an INP (Impulse Noise Protection) value. 3.The transceiver of claim 1, wherein the receiver is capable ofdetermining the repetition rate based on impulse noise measurements. 4.The transceiver of claim 1, wherein the receiver is capable ofdetermining the repetition rate based on crosstalk measurements.
 5. Amulticarrier transceiver comprising: a receiver capable of determining arepetition rate for DMT (Discrete Multitone Modulation) symbols; atransmitter capable of transmitting a first message duringinitialization, wherein the message indicates the repetition rate; thetransmitter further capable of transmitting a second message duringinitialization, wherein DMT symbols in the second message are repeatedin accordance with the repetition rate indicated in the first message,and wherein the message comprises a plurality of CRC (Cyclic RedundancyCheck) bits and wherein at least one DMT symbol in the second messagecomprises one CRC byte and no information bits.
 6. The transceiver ofclaim 5, wherein the receiver is capable of determining the repetitionrate based on an INP (Impulse Noise Protection) value.
 7. Thetransceiver of claim 5, wherein the receiver is capable of determiningthe repetition rate based on impulse noise measurements.
 8. Thetransceiver of claim 5, wherein the receiver is capable of determiningthe repetition rate based on crosstalk measurements.
 9. A non-transitorycomputer-readable information storage media, having stored thereoninstructions, that when executed by one or more processors in atransceiver, cause to be performed a method comprising: determining, bya receiver, a repetition rate for DMT (Discrete Multitone Modulation)symbols; transmitting, by a transmitter, a first message duringinitialization, wherein the message indicates the repetition rate;receiving, by the receiver, a second message during initialization,wherein DMT symbols in the second message are repeated in accordancewith the repetition rate indicated in the first message, and wherein themessage comprises a plurality of CRC (Cyclic Redundancy Check) bits andwherein at least one DMT symbol in the second message comprises one CRCbyte and no information bits.
 10. The non-transitory computer-readableinformation storage media of claim 9, wherein the determining of therepetition rate is based on an INP (Impulse Noise Protection) value. 11.The non-transitory computer-readable information storage media of claim9, wherein the determining of the repetition rate is based on impulsenoise measurements.
 12. A non-transitory computer-readable informationstorage media, having stored thereon instructions, that when executed byone or more processors in a transceiver, cause to be performed a methodcomprising: determining, by a receiver, a repetition rate for DMT(Discrete Multitone Modulation) symbols; transmitting, by a transmitter,a first message during initialization, wherein the message indicates therepetition rate; transmitting, by the transmitter, a second messageduring initialization, wherein DMT symbols in the second message arerepeated in accordance with the repetition rate indicated in the firstmessage, wherein the message comprises a plurality of CRC (CyclicRedundancy Check) bits and wherein at least one DMT symbol in the secondmessage comprises one CRC byte and no information bits.
 13. Thenon-transitory computer-readable information storage media of claim 12,wherein the determining of the repetition rate is based on an INP(Impulse Noise Protection) value.
 14. The non-transitorycomputer-readable information storage media of claim 12, wherein thedetermining of the repetition rate is based on impulse noisemeasurements.
 15. A multicarrier transceiver comprising: a receivercapable of determining, during initialization, a repetition rate for DMT(Discrete Multitone Modulation) symbols; a transmitter capable oftransmitting a first message during initialization, wherein the messageindicates the repetition rate; the receiver further capable of receivinga second message during initialization, wherein DMT symbols in thesecond message are repeated in accordance with the repetition rateindicated in the first message, wherein the message comprises aplurality of CRC (Cyclic Redundancy Check) bits, wherein at least oneDMT symbol in the second message comprises one CRC byte and noinformation bits.
 16. The transceiver of claim 15, wherein the receiveris capable of determining the repetition rate based on an INP (ImpulseNoise Protection) value.
 17. The transceiver of claim 15, wherein thereceiver is capable of determining the repetition rate based on impulsenoise measurements.
 18. The transceiver of claim 15, wherein thereceiver is capable of determining the repetition rate based oncrosstalk measurements.
 19. A multicarrier transceiver comprising: areceiver capable of determining, during initialization, a repetitionrate for DMT (Discrete Multitone Modulation) symbols; a transmittercapable of transmitting a first message during initialization, whereinthe message indicates the repetition rate; the transmitter furthercapable of transmitting a second message during initialization, whereinDMT symbols in the second message are repeated in accordance with therepetition rate indicated in the first message, and wherein the messagecomprises a plurality of CRC (Cyclic Redundancy Check) bits and whereinat least one DMT symbol in the second message comprises one CRC byte andno information bits.
 20. The transceiver of claim 19, wherein thereceiver is capable of determining the repetition rate based on an INP(Impulse Noise Protection) value.
 21. The transceiver of claim 19,wherein the receiver is capable of determining the repetition rate basedon impulse noise measurements.
 22. The transceiver of claim 19, whereinthe receiver is capable of determining the repetition rate based oncrosstalk measurements.